Strand/preview testing of hair allows the professional stylist to observe and accurately determine: (1) a hair color formulation (2) the timing required to achieve the desired result (3) whether pre - or - post treatment will be necessary, or give a pass/fail procedure evaluation based on final hair integrity. The test area is usually selected from an area of hair below the occipital line, unless color data from the crown of the head is needed to complete the formulation process. Strand/preview testing also allows the stylist to determine if there are any outside influences that could affect the ultimate result. Outside influences that can affect results include the use or presence of sulfur-based medicines or topical creams, vitamins, minerals, shampoos for dandruff or psoriasis, vegetable tints, henna, and/or metallic-based dye. Or it can be environmentally based such as the heat or air conditioning drafts in the facility.

Allergy to aniline derivative tint is unpredictable. Some clients are already sensitive while others may develop an allergic response after years of successfully receiving color services. Sensitivity may also arise in conjunction with other health issues. It is important to identify allergic clients. Before applying an aniline derivative tint, a patch or predisposition test should be conducted. The test results should be negative, showing no swelling, burning, itching, or blisters.

Standard: Cosmetology schools and hair color manufacturers recommend this safety procedure, which is printed on or in every instruction document and text book. The U.S. Federal Food, Drug, and Cosmetic Act prescribes that a patch or pre-disposition test must be given 24 - 48 hours prior to each application of an aniline tint or toner. The test used for the skin must be the same formula as that is used for the hair coloring service. The hair stylist should perform the test gloved.

(Note: There is no test for reaction to inhaled fumes other than exposure to the mixed active product.)

As you can see these two tests are separate, individual, and non-competitive. Both tests are strongly "recommended" as necessary and required industry wide.